Method of evaporating fish extract



I! Patented Feb. 3, 1942 Henry L.

Pollard, Petaluma, Calif., assignor to Western Condensing Company, San Francisco, Calif., a corporation of California Application my 11,1939, Serial a... 214,220

comma wine-m This invention relates generally to processes for the. evaporation of fish extract, particularly fish extract produced-in connection with fish re-.

ductlon plants. d I In flsh'processing orv fish reduction plants,

sible to control or "practically eliminate scale formation asdescribedabove; f

Further objects of the invention will appear 9 from the following description in whichthe premaking use of fish having arsubstantial oil con- I a tent such as mackerel, sardines, herring, or

menhaden, it is common to treat the fish in suitablesteam cookers, after which they are subjected to mechanical-pressure in a suitable press toexpress a largepercentage of the liquid content. This liquid material is a mixture of oil and aqueous fractions, together with considerable water I soluble solids, and someundissolved solids.

Insofar as 'feasible' the--undissolved-..so1ids are ferredembodiment of the inventionhas been set forth indetail.

Referring to the drawing:

Fig l is a diagrammatic flow sheet illustrating one embodiment of the, method.

. "Fig. 2 is another diagrammatic flow sheet 11- lustrating a modification of the method.

, My invention ispredicated upon. the discovery {theta small amount of alum introduced into "stick water, has a remarkable effect upon scale removed bysuitable processes such as settlement I ,ratorof. thetype disclosed inthe aforesaid Pat- I ent No. 2,090,985, andthe-efllcie'ncy and capacity or filtration. The liquid material is-then sub- I iected toa series of:separating,operationsgwhich in most approved practices makes use of a battery of-centrifuges, whereby valuable fish oil is removed from the aqueous fraction. The resulting aqueous fraction is commonly referred to as stick water and it consists largely of water, together with dissolved solids, a variable but usual-- 1y small" amount of suspended solids, and a very small quantity of remaining oil.

' Stick water has presented a serious disposal problem to the fish industry, particularly when it is endeavored to convert the'stick water into saleable by-products. One method of disposal is to concentrate the stick water by evaporation, after which it is converted to a dried material as by spray drying, or by intermixture with other solids of a fibrous nature, Concentration of stick water by evaporationhas been found to be a difficult operation, due to the fact that a hard scale rapidly forms upon the heated surfaces of the evaporator with which the .material is contacted. For example when using an evaporator of the type disclosed and claimed in Peebles and ManningPatent No. 2,090,985, scale formation uponthe-inner surfaces ofthe evaporating tubes rapidly decreases the capacity of the equipment. As a resultin'commercial operations where stick water is evaporated, the evaporator-s must be frequently shut, down fortheremoval of accumulated-scale, which is a dillicultoperation requiring use of wire brushes and/orstrong acids. Also due to impairedcapacity over agiven Operating period the size ofthe evaporating equipment must be relatively large for a" given scale of operation. I a

It is an object of the present inventionto provide a novel method for the concentration 01' formation. For example I have found that when sitick water v is being concentrated in an evapoof the equipment has beenfsubstantially impaired byi scale formation, a small amount ot .alum introducedlnto the stick water being supestick water by evaporation, which makes it pos- 55 plied to the evaporator, causes a rapid increase in capacity. I have found that this treatment prevents scale formation, which as previously explained, is the principal cause for decreased capacity and impaired operation. I have also found that small amounts of alum continually intermixed with stick water being evaporated, cause a substantial absence of'scale formation on the evaporating tubes over long operating periods.

In practice I prefer to makeusebfbommun alum (aluminum sulphate), which is initially dissolved in water. This solution is added to and mixed with the stick water as it passes to the evaporator.

As shown in Fig. 1 of the drawing where the stick water is flowing continually through a pipe II from the centrifugal separating equipment II,

the alum solution can be introduced continually into the same pipe, under the control of a suitable proportional feeder I2, after which the mixture can be passed through a pump l3 which insures thorough intermixture, and then delivered to the evaporating equipment it. It has been found that with stick water obtained from reduction of California sardines, about 0.25% (by weight) of alum (Alzi 8003182120) will give good results in inhibiting scale formation. Larger amounts of alum can be used if desired, although such practice is not-recommended since the cost of the process is'increased without particular benefit.

Another manner of practicing the invention with the general procedure of Fig. 1 is to introduce the alum intermittently, for the purpose of controlling scale formation. Thus after handling a certain amount of the material, such as is known to cause scale formation to a substantial degree, one may introduce a solution of alum prepared as described above, by way of feeder II, for a period of time sufficient to reduce or practically eliminate accumulated scale.

Another embodiment of the invention" shown in Fig. 2 is to keep a certain amount of stick water in a separate container 85, to which alum has been added, and which is available for use in removing scale. where stick water is being evaporated in equipment l4, the flow of materialyfrom, the main source of supply is interrupted when it is desired to reduce or remove scale from the evaporator tubes, and the stick water with alum supplied to 1-,;

the evaporator through line II. The concentrate from the evaporator is returned through line ll to the separate container It and water added as v v indicated to take the place of water evaporated.

This procedure avoids the presence of alum in the final product and reduces alum consumption to a minimum. During normal operation circulation through tank It is interrupted and the concentrate is removed as indicated by line ll.

Alum is an efiective, coagulant, which is nontoxic in small amounts, and which is capable of Thus in'plant operations I surfaces.

tion or condition present in the stick water info which alum has been introduced, which I attribute to the presence of flsh proteins, and which serves to inhibit and remove scale formation.

Since the present invention makes possible operation oi evaporating equipment at maximum capacity, it will be apparent that for a given scale of plant operation, the evaporating equipment need not be of abnormal size. In addition, shut down of the equipment for-the purpose of removing scale, can be eliminated or reduced to a minimum, to effect a substantial saving in maintenance and labor. All of these factors contribute to lower over-all cost in converting stick water into saleable by-products. Although alum appears in'the final product the amount present can be sumciently small as to have no detrimental biological efl'ects.

Iclaim:

1. In a method for the concentration of stickwater by evaporation, where the evaporation is effected by contact 0; thestmk water with heated surfaces, the step oiint'roducing alum into the stick water to inhibit or"removescale'ilormition t atignyof stick .1: si fi s' 18 eflected by contact of the stickwatefwith heated surfaces, the step of introducing' alum'into the stick water in amounts of'theprder' ot"about 0.25% or more by weightth alum serving'to inhibit or remove seine 1ormation on'*thefheated 3. In a method {or the concentration jot stick water by evaporation, where the "evaporation is eflected by contactof the stick'water with heated surtaces, the'step or contacting the heated surfaces with a liquid'material containing fish proteins and alum whereby scale'i'ormation is inhibited or removed.

HENRY L. 

